Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$112.35	10.264%	$123.8816	$123.88	$123.90	$123.90
Purchase #2	$72.86	9.278%	$79.62	$79.62	$79.60	$79.60
Purchase #3	$134.82	10.449%	$148.9073	$148.91	$148.90	$148.90
Purchase #4	$103.99	7.681%	$111.9775	$111.98	$112.00	$112.00
Purchase #5	$114.35	11.386%	$127.3699	$127.37	$127.35	$127.40
Purchase #6	$155.40	10.644%	$171.9408	$171.94	$171.95	$171.90
Purchase #7	$182.58	7.154%	$195.6418	$195.64	$195.65	$195.60
7 purchase totals =	$876.35		$959.3389	$959.34	$959.35	$959.30